The epidemiology of ocular trauma has been described extensively in the United States and other parts of the world.⁶ However, a comparison of different studies is often difficult because ocular trauma comprises a spectrum of disorders with wide variations in etiology and clinical presentation. In addition, the frequency and burden of eye injury is highly dependent on the research strategy, the population studied, and the nature of the data. This chapter provides a broad review of the scope of ocular trauma, unique epidemiologic characteristics, and the impact of ocular injuries from a population perspective.

TABLE 56-1. Incidence of Ocular Trauma

Location Setting	Population Studied	Type of Data	Case Definition of Ocular Trauma	Annual Incidence Rate per 100,000 Population
Alabama(1982-86)9	All ages	Prospective trauma registry	Severe injury	7.7
Maryland (1979-86)10	All ages	Hospital discharge data analysis	Principal hospital discharge diagnosis (principal and secondary discharge diagnoses)	13.2 (27.3)
United States(1984-86)11	All ages	Hospital discharge dataanalysis	Principal hospital discharge diagnosis (principal and secondary discharge diagnoses)	13.2 (29.1)
Stockholm, Sweden(1974-79)20	All ages	Retrospective studyusing hospitalization case records	Injury requiring hospitalization	6.1
Scotland (1991-92)21	All ages	Prospective study on all eye trauma hospitalizations	Injury requiring hospitalization	8.1
Victoria, Australia(1989-91)22	All ages	Prospective study onall eye trauma hospitalizations	Injury requiring hospitalization	15.2
Papua New Guinea(1984-95)28	All ages	Retrospective study onall eye clinic visits related to trauma	Medically treated injury	39
Wisconsin(1978-79)13	All ages	Prospective study on eyecasually room visits	Medically treated injury (injuryrequiring hospitalization)	420 (47)
Newcastle, England(1992)24	All ages	Prospective study on eye casually room visits	Medically treated injury (injuryrequiring hospitalization	720
Baltimore (1985-88)17	40 yr	Population-based interview	Any injury (medically treated injury)	490 (400)
New England (1985)16	18 yr	Population-based interview	Medically treated injury	980
California (1988)12	All employed persons	Hospital discharge data and workers compensation claims analysis	Principal hospital discharge diagnosis plus workers compensation as the principal source of payment (principal and secondary discharge diagnoses)	1.8 (3.0)
Maryland (1982)62	16 yr	Hospital discharge data analysis	Principal hospital discharge diagnosis	15.2

Eye injury registries can be an important and useful source of information if they are linked to a population perspective. The National Eye Trauma System (NETS) registry collected data on open globe injuries in 48 collaborating centers in 28 states⁷ and provided basic demographic, clinical, and etiologic information on these severe injuries. However, participation in the NETS is voluntary, only penetrating injuries are reported, and estimates of population burden are not available because ascertainment of these injuries is not complete for a defined population. Similarly, the Eye Injury Registry of Alabama collects information only on severe eye injuries and is not compulsory.^8,9 Morris's study reported an annual incidence of severe ocular trauma with significant anatomical or structural damage of 7.7 per 100,000.⁹ In comparison, a Swedish study estimated an annual incidence of 6.1 per 100,000 for open globe injuries.²⁰

Hospital discharge data are another source of information on ocular injury and can provide good estimates of ocular injury incidence.^10–12 In both Maryland and the United States as a whole, using a definition of a principal hospital discharge diagnosis of ocular injury, the annual incidence was estimated to be 13.2 per 100,000. If secondary discharge diagnoses of ocular trauma were included, the incidence was between 27.3 and 29.1 per 100,000 per year. Hospital discharge data have shown a decline in admission for ocular trauma over time, with a 25% decline in incidence of hospitalization for ocular trauma from 1979 to 1986. This appears to be related to changing indications for hospitalization, especially for traumatic hyphema.¹⁰ Even in the United States, there is significant regional variation in the incidence of hospitalization for ocular trauma. For example, the New England and Pacific regions were found to have age- and gender-adjusted rates 25% or more below the national average, but the West North Central region had a rate 40% above the average.¹¹ Comparable data are available from other countries. A prospective study on all patients admitted to Scottish hospitals for ocular trauma indicated an annual incidence of 8.1 per 100,000 individuals.²¹ A study in Victoria, Australia estimates an annual incidence of eye injuries requiring hospitalization of 15.2 per 100,000.²² Different standards of clinical practice among countries and hospitals likely affect the rate of hospitalization as well as other factors, such as age and socioeconomic distributions.

Data at eye emergency departments in hospitals capture eye injuries that usually need immediate medical attention. Because a large number of such cases are relatively minor injuries that do not require hospital admission, they provide a broader perspective on the problem at the population level than do hospital discharge data. An important prerequisite in estimating incidence using data from eye emergency departments is a well-defined population served by a single hospital or a few hospitals, and reasonable justification that the population will not seek treatment elsewhere. Karlson and Klein reported on patients with ocular trauma, seen in emergency rooms or in hospitals, among residents of Dane County, Wisconsin, and estimated an incidence of 420 per 100,000 per year, of which only 11% were admitted to a hospital.¹³ These data suggested an incidence of hospitalization of 47 per 100,000, about four times higher than in either Klopfer's or Tielsch's study. However, the total number of hospitalizations was extremely small and a direct comparison is difficult to make because ocular injury was not the usual reason for hospitalization. At the University Hospital of Umea in Sweden, 927 eye injuries were treated during a one year period, an estimated annual incidence of 810 per 100,000 population.²³ A prospective study on all patients presenting to eye casualty services in Newcastle, England showed an annual incidence of 720 per 100,000²⁴; caution should be exercised in interpreting this figure, however, because the study was conducted during a period of 8 weeks. Although incidence rates cannot be calculated from most other studies because of a lack of a well-defined denominator, they provide valuable information on the etiology, severity, and consequences of ocular injury.^14,15,25

Population-based studies provide data on injuries not requiring medical attention at emergency rooms or admission to hospitals and better reflect the burden of this problem in the population. Two such studies have used questionnaires to estimate the incidence of ocular injuries.^16,17 Glynn and colleagues surveyed a randomly selected New England population 18 years of age or older and found an annual incidence of 980 ocular injuries per 100,000 individuals.¹⁶ This suggested that more than 90,000 eye injuries require medical attention annually in New England alone. Katz and Tielsch estimated a rate of 400 per 100,000 in a population 40 years of age or older from the Baltimore Eye Survey.¹⁷ This was similar to an incidence of 300 per 100,000 in Glynn's study for individuals more than 40 years of age.¹⁶ An additive risk of ocular trauma occurred with age; the cumulative lifetime prevalence of ocular injury was nearly 15%.¹⁷

Limited information is available regarding the incidence of ocular trauma in developing countries. Blindness prevalence studies have indicated that ocular trauma does not appear to be a major problem^26,27; however, such surveys usually contain detailed examinations for only those subjects who have bilateral vision loss, thus excluding most ocular injuries, which are unilateral. A recent retrospective chart review of all ocular trauma cases seen in Papua New Guinea estimated an incidence of 39.1 per 100,000.²⁸ A survey of patients admitted to a hospital for ocular trauma in Malawi, in south-east Africa, showed that eye trauma was relatively common, occurring most frequently in children, young adults, and males.²⁹ Most of the injuries occurred under domestic circumstances and were associated with chopping and gathering wood.

BLINDNESS AND OTHER CONSEQUENCES FROM OCULAR TRAUMA

The ocular morbidity and burden of ocular trauma are enormous. As noted earlier, bilateral blindness rates do not provide an accurate population-based perspective of the burden of ocular trauma because of the unilateral nature of the disease. Sommer and coworkers found in the Baltimore Eye Survey that the prevalence of bilateral blindness caused by ocular trauma was 75 per 100,000 and that eye injuries accounted for only 5.6% of blind eyes among all bilaterally blind persons.¹⁸ Although the study found no case of bilateral blindness caused by ocular trauma in whites, 9.5% of blind eyes among bilaterally blind black persons were from trauma. Another source of data is the Model Reporting Area Study (MRA), which collected information from 16 states in the United States that agreed to a common format and definition for reporting blindness registration. Injury or poisoning accounted for 3.6% of all incident cases of blindness, with an annual incidence of blindness registration from ocular injury of 0.48 per 100,000 in 1970.¹⁹ This was significantly lower than rates estimated in the Baltimore Eye Survey,¹⁸ in part because of the incomplete ascertainment of blind persons in the MRA system. In other countries, the rate of bilateral blindness from ocular trauma is also small. In a Scottish study, no patient was registered blind on discharge from the hospital during the one year study period.²¹ The Israeli Ocular Injuries Study found that bilateral blindness occurred in only six out of 2,276 patients (260 per 100,000) hospitalized for ocular injuries.³⁰ In Sweden, an annual incidence of 6.1 per 100,000 for potentially blinding open globe injuries was reported.²⁰ Limited information is available about actual rates of ocular injury in developing countries but blindness prevalence surveys indicate that the absolute rates of blindness from trauma appear to be small. In Nepal, 860 per 100,000 people had either a history or clinical signs of trauma, but less than 40% had any visual impairment.³¹ Only 2.4% of cases of bilateral blindness, or an absolute prevalence of 20 per 100,000, were due to trauma; this rate is approximately three times lower than the prevalence found in the Baltimore Eye Survey.¹⁸ Population-based studies conducted in Africa failed to find any cases of bilateral blindness caused by trauma.^26,32 Although accurate estimates of the prevalence or incidence of blindness from ocular trauma in most populations are still not available, it would appear that ocular injuries play a relatively minor role in the etiology of bilateral blindness.

Although ocular trauma accounts for only a small proportion of cases of bilateral blindness, it is an important cause of monocular blindness. In rural Kentucky, trauma accounted for 40% of monocular blindness, or a population prevalence of 13.2 per 1000.³ In east Baltimore, the prevalence of trauma-associated monocular blindness was 6.6 per 1000¹⁷ and in Nepal, 2.4 per 1000.³¹ Of patients admitted to a hospital for ocular trauma in the Scottish study, 10.7% were unilaterally blind at discharge.^21,33 Because blinding ocular injuries are often associated with multiple organ injuries with high case fatality, cross-sectional surveys underestimate the magnitude of this problem.

From a public health perspective, neither bilateral or unilateral blindness rates provide a complete context of ocular trauma for society. Another important viewpoint is reflected in the economic costs associated with ocular injury. Severe ocular trauma requires expensive hospitalization and specialist treatment, and often prolonged follow-up and visual rehabilitation. An overall picture of the economic burden requires an estimation of both direct costs of treating ocular injuries and indirect costs resulting from the injuries (such as time lost from work and family caregiving).

Direct costs of ocular trauma have been investigated by Tielsch and Parver. They estimated that more than 227,000 hospital days and approximately 200 million dollars in hospital charges may be directly related to hospitalization for ocular injuries each year, based on Maryland hospital discharge data.³⁴ Even these figures on direct costs may be considered an underestimation because physician fees, investigation charges, follow-up charges in the outpatient setting, and medications were not included in these totals. In addition, Veterans Administration hospital admissions were not included in the calculations in this study.

The indirect, secondary economic impact of ocular trauma is harder to estimate. Work-related ocular injuries usually affect young adults who are in their most productive years. Three quarters of work-related open globe injuries reported in the NETS study occurred in individuals less than 40 years of age.⁷ Schein and colleagues observed that patients with open globe injuries had an average of 70 days of medical leave from work and that 40% of those with open globe injuries sustained at work were pursuing costly legal action against their employers.¹⁵ Munoz estimates that in the United States, around 5 million dollars is spent on ocular trauma in direct and indirect costs per urban trauma center.⁵ Similar economic burdens can be expected in other developed countries. Fong estimated that 155 million dollars a year may be spent on hospitalization for the estimated 116,000 annual cases of ocular injury in Australia.²² The full socioeconomic impact of ocular injuries must be studied further to provide a more complete picture of the public health significance of ocular trauma.

AGE

High rates of ocular injury in young adults have been observed consistently in nearly all descriptive^7,14,15,25 and controlled epidemiologic studies.^{10–12,17,22,33} This high incidence reflects a high proportion of work-, assault-, sports-, and motor vehicle crash-related ocular injuries in the young adult age groups, particularly among young men. However, hospital discharge data on ocular injuries in Maryland and in the United States suggest that a substantially higher than average risk of trauma occurs in the elderly as well.^10,11 The age and gender pattern observed in Maryland is characteristic of the epidemiology of ocular trauma (Fig. 1) and reveals two important features. The age-incidence curve is bimodal for both males and females, with a well-recognized peak in incidence from about 18 to 25 years of age and an additional peak after age 70. For females, this peak in incidence after age70 is three times higher than the peak in young adulthood, but the peak in elderly men is similar to that observed for men in their twenties. This higher incidence among the elderly is also observed nationally¹¹ but is not usually reflected in other studies because either all elderly are grouped over age 60 or 65, or because small sample sizes preclude accurate estimation in this age range.^{9,13,16,30,35}

GENDER

The second unique epidemiologic feature of ocular trauma is that the higher risk among men occurs across the full age range until age 70, when the gender-specific curves merge. The higher risk among men has been found in every population-based study of ocular injuries, with incidence or prevalence ratios (male:female) from two to greater than five.^{9–11,13,16,17,24,30,35} This difference between men and women disappears after the age of 70, and may be related to a change in lifestyle and occupational patterns among men after this age.

RACE AND SOCIOECONOMIC STATUS

Racial variations in rates of ocular injury have been observed but likely reflect variations in socioeconomic status and not race alone. In Maryland, nonwhites had higher rates of hospitalization for ocular injury overall, with a 40% to 60% higher risk compared with whites between the ages of 25 and 65.¹⁰ Higher rates were also observed in the Baltimore Eye Survey data for injuries associated with vision loss. African American men had rates of ocular injury three or four times higher than those of white men, whereas African American women had rates between 30% and 90% higher than those of white women, depending on the severity of vision loss.¹⁷ In Brazil, children from lower socioeconomic strata were found to have higher frequencies of ocular trauma compared with those from higher socioeconomic strata.³⁶

There is no ideal classification of ocular trauma etiology. One classification is based on location and activity at the time of injury (e.g., at work, in the home, during sports, or while commuting). Other studies provides detailed information on the source and nature of injury (e.g., grinding, sharp instruments, falls, BB guns, or fireworks). Table 2 summarizes the common settings in which ocular trauma occurs. Work-related injuries are usually the most common cause of ocular trauma, followed by home-related injuries, and injuries from sports and recreation, assault, and travel.

TABLE 56-2. Etiology and Site of Ocular Trauma

Eye injuries in a variety of settings are preventable with current, inexpensive protective devices and simple modification of the environment. This is true for many work-related injuries, sports-related injuries, motor vehicle crashes, and injuries from BB guns and fireworks. Modern injury prevention theory does not support the claim that injuries are “accidents” or “bad luck”. Most ocular trauma occurs in well-defined, predictable, and consistent settings and is therefore potentially preventable.

WORK-RELATED INJURIES

Work-related injuries are important for two reasons. First, they occur in the adult working population and therefore carry significant economic implications. Secondly, work practice legislation and environmental modification offer tremendous potential for primary prevention. Case series and eye registry data in the United States have indicated that work-related injuries constitue between 22% and 50% of all ocular trauma.^7–9,15 In Australia, a study estimated that 42% of ocular injuries were work-related³⁷; in the United Kingdom, a study puts the proportion of occupation-related eye injury at 70%.²⁵ The limitations of these series include a lack of well-defined denominators and, therefore, an inability to calculate rates.

Data on the incidence of eye injury in the workplace, however, is limited. A California statewide study using hospital discharge data estimated an annual incidence of severe ocular injury in the workplace of 1.76 and 2.98 per 100,000 employed persons, when ocular trauma was the principal discharge diagnosis and the principal or secondary discharge diagnosis respectively.¹² A study in Wisconsin on patients seen at emergency departments estimated an incidence of work-related eye injuries of 55 per 100,000.¹³ Population-based studies yield much higher rates. One such study in New England estimated the annual incidence of eye injuries occurring at work to be approximately 600 per 100,000 persons.¹⁶ In Italy, Cruciani and associates analyzed a national insurance database that registers all casualties that cause work disabilities exceeding 3 days, and reported an annual incidence of ocular injury of 370 per 100,000.³⁸

Projections to the entire U.S. population from the California data indicate that between 2,165 and 3,745 acute hospitalizations for work-related ocular trauma occur each year.¹² However, less severe work-related eye injuries not requiring acute hospital admission are equally important because of direct and indirect costs related to their treatment, as well as the fact that minor eye injuries are often preventable with the use of simple protective eye wear and modification of worksite environments. Of the 900,000 occupational eye injuries estimated by the National Institute for Occupational Safety and Health to have occurred in 1982, 84% were classified as minor.³⁹ In the Wisconsin study, 97.8% of the 188 cases of work-related trauma were classified as minor or moderate.¹³

There is a paucity of data on industry-specific rates of ocular injury. Schein and associates observed that 63% of occupation-related injuries occurred among workers in the construction industry and 18% occurred among auto repair workers.¹⁵ In a U.K. study of the chemical industry, an incidence of 2,300 ocular injuries per 100,000 worker-years was observed, with only 22% of these injuries requiring medical attention.⁴⁰ Only 45% of these injuries were chemical injuries, indicating that most of them could have occurred in any number of industrial settings.⁴¹ A survey on 1552 firemen in the U.K. fire service indicated an annual incidence of 3,500 ocular injuries per 100,000 firefighters.⁴² In Finland, industry-specific data showed that iron and steel, fabricated metal manufacturing, and excavating and foundation industries have the highest annual incidence of ocular injuries at 680 per 100,000 workers.⁴³ In Australia, automotive industry workers had the highest relative incidence of open globe injuries compared with other occupations but these workers were also the least likely to wear safety eye-wear.³⁷ An injury surveillance system in a large U.S. automotive corporation estimates an annual incidence of 1,500 eye injuries per 100,000 employees in the corporation's factory plants (Wong TY, Lincoln A, Baker S: Epidemiology of ocular injury in a major automobile corporation. Presented at the National Occupational Injury Research Symposium, Morgantown, West Virginia, Oct 1997).

The military represents a high-risk occupational group. In two reports, the proportion of ocular injuries among soldiers has been observed to be between 1.7% and 2.4% of all training injuries.^44,45 U.S. Army hospital discharge data indicate that between 1985 and 1994 5450 military personnel were hospitalized with a principal or secondary discharge diagnosis of ocular injury, an average annual incidence of 77.1 per 100,000 (unpublished data). This is almost 30 times higher than the rates estimated by Baker and associates for all occupational eye injuries in California.¹² Surprisingly, the rate of ocular injury was highest in whites and lowest in nonwhite-nonblacks, but in Baker's study, Hispanics had a higher risk of injury than any other ethnic group.¹² The fact that assault was the single most common source of eye injury in the military highlights the role of off-duty activities and high risk behavior in this population.

Many studies have shown that adequate eye protection in the workplace can prevent many serious eye injuries and makes economic sense. A major problem is compliance among workers. This is related partly to poorly designed and uncomfortable eyewear. More attention directed to the development of ergonomic protective eyewear for use in occupational settings and delineation of high risk occupational groups will aid prevention of work-specific injuries.

HOME-RELATED INJURIES

Home-related injuries account for a substantial proportion of ocular trauma in virtually all reported studies (see Table 2). The magnitude of this problem is difficult to estimate because of a lack of a common definition of home-related injury. Nevertheless, numerous reports have shown that ocular trauma at home constitutes between 15% and 41% of all ocular injuries.^{9,14,15,20,25} In another study, among patients with open globe injuries presenting to Wills Eye Hospital, the home was the most common setting for ocular injury.⁴⁶

The exact nature of home-related trauma has not been described in detail. Macewen reported that 18.3% of the 5671 patients presenting to eye emergency departments in Glasgow had home-related injuries.²⁵ Of these injuries, nearly 20% occurred in children less than 10 years of age. Being struck by a large object was the most common cause of these injuries, followed by small foreign bodies entering the eye. The home accounted for 30% of serious eye injuries in another U.K. study and was the most frequent place of injury for those less than 15 years of age and those 65 years of age and older.³³ Hammers, nails, drills, and other hand tools are important etiologic components of these injuries.

Unlike work-related injuries, which can be prevented with modification of the work place and the use of eye protection, it is unclear how home-related ocular trauma should be tackled. Limited data suggest that the young and the elderly are particularly at risk for home-related injuries and have important implications for prevention. Safety and preventive strategies specifically aimed at eye injury should now include the home as a high risk environment, in addition to the traditional workplace and sports facilities. There may be a need for review and revision of safety standards for household products such as toys, tools, aerosol cans, and kitchenware. Patient education regarding the dangers of home equipment may be another preventive approach.

SPORTS-RELATED INJURIES

Because of the rise in the popularity of sports and a growing emphasis on healthy lifestyles worldwide, sports-related ocular trauma represents an increasingly common eye health hazard. In the United States, it is estimated that eye injuries from sports account for more than 100,000 physician visits per year, at the cost of more than 175 million dollars.⁴⁷ The absolute rate and proportion of total injuries varies greatly by age, gender, the case definition of ocular injury, and the population studied. Not surprisingly, sports-related injury accounts for a large proportion of all injuries in the young age groups, especially in males, but becomes insignificant with age. Although as many as one quarter of all severe injuries in registry-based studies are sports-related,^8,9 population-based hospitalization data suggest that sports play a relatively minor role and are responsible for less than 10% of all eye injuries.^10,11

The specific sports commonly responsible for injury vary among cultures and populations. The sports responsible for the greatest number of injuries in the United States are baseball, ice hockey, and racquet sports.⁴⁷ An estimated 189 million individuals participate in these sports in the United States alone. Other sports that account for significant numbers of ocular injuries include boxing, street hockey, and basketball. In Ireland, a survey of ocular sports injuries in an eye casualty department found that hurling was responsible for 30% of the injuries and that soccer accounted for 29%.⁴⁸ An analysis of eye casualty department data from U.K. hospitals shows that racquet sports, namely tennis, badminton, and squash, were the most common causes of sports-related ocular injuries.⁴⁹ Floor ball was responsible for 46% of patients with blunt trauma seen at the University Eye Hospital of Lund in Sweden,⁵⁰ and squash, badminton, Australian-rules football, and cricket were the most common causes of sports-related ocular injury in Australia.⁵¹

The mechanisms of ocular injury are multiple. In baseball, both the hardness and velocity of the ball can potentially cause serious orbital, ocular, and facial injuries, especially among batters.⁵² Similarly, in racket sports, the tremendous speed of the ball can penetrate even open-lens eye guards.⁵³ Accidental impact with the racket frame also can lead to significant injury. In basketball, most injuries occur from physical contact with other players. Of the 59 ocular injuries sustained by National Basketball Association players during a 17-month study, nearly a third of the injuries occurred while the player was in the act of rebounding; another third occurred while the player was on offense.⁵⁴ Most injuries were caused by fingers (35.6%) or elbows (28.8%).

Another high-risk sport is boxing. Retirements of a number of professional boxers after ocular trauma have given much publicity to this kind of injury. However, significant risks are often incurred by amateur boxers. One study found that among asymptomatic amateur boxers, 24% had retinal breaks; another study recorded potentially sight-threatening injuries in 58% of asymptomatic amateur and professional fighters.^55,56

A recent article indicated that the most common sports-related injuries were minor abrasions and contusions, followed by more serious injuries, including hyphema.⁴⁷ Despite the relatively small risk of severe sports-related ocular injury, the literature on this subject is vast.⁵³ The principal reason for this interest among public health professionals and ophthalmologists is that nearly all sports-related injuries are preventable. A classic, often cited example is the 90% decline in the incidence of ice hockey-related ocular injury in Canada after introduction of mandatory use of appropriate helmets and eye protection.^56,57 Almost any sport can benefit from primary prevention with simple eye protective devices. In baseball, polycarbonate or wire-mesh face protectors added to batting helmets can almost eliminate the risk of severe ocular injury. In racquet sports, studies have clearly documented the benefits of using polycarbonate, closed-lens eye guards for the prevention of injury, with many sports clubs opting for compulsory use of protective eyewear during games.⁵³ As for boxing-related injuries, whether better design and increased use of headgear, thumbless gloves, or heavier gloves can reduce risks has yet to be shown. More than 95% of the National Basketball Association players who experienced ocular trauma were not wearing protective eyewear at the time of injury.⁵⁴ Clearly, the awareness of the general public concerning the use of eye-protectors is inadequate and more work in the area of prevention is needed. Polycarbonate plastic lenses and frames that are sturdy and impact resistant provide optimal protection but lensless goggles, street wear, and standard spectacles provide inadequate eye protection. Increasingly active participation from all eye care professionals in the prevention of sports-related eye injuries, including addressing particular sports participants' needs, identifying one-eyed athletes, and continuing education regarding the need for protective eyewear is necessary.

ASSAULT

Assault is another important factor in the etiology of ocular injury, especially among young adults in urban environments. It is the single most common, well-defined cause of a principal discharge diagnosis of ocular trauma, accounting for 18% of cases overall in the Maryland hospital discharge study.¹⁰ The data showed that, among nonwhites, assault accounted for more than 28% of cases, but that it accounted for only 13% among whites. The high frequency of assault is reflected on a national basis as well, accounting for more than 10% of all hospital discharges for ocular trauma.¹¹ In urban areas, assault accounts for as much as 40% to 50% of cases presenting to eye emergency rooms.^14,27 Liggett suggests that the high proportion of assault-related injuries appears to be correlated with populations that have a high homeless rate, low socioeconomic status, and high unemployment.¹⁴ Other studies from tertiary referral centers and regional trauma centers in different settings show that assault is responsible for fewer injuries (8% to 15%), partly because of the wider patient catchment area¹⁵ and partly because of a concentration in trauma centers of victims with multiple system injuries.⁵⁸ Assault-related injuries are usually severe and associated with significant visual morbidity. Eighty percent of eyes with no light perception and 60% with an initial acuity of 20/200 were injured from assault in one study.¹⁴

Traditional preventive measures used in the workplace, such as eye protection, are not useful in cases of assault, and novel approaches are needed in violence prevention to reduce the burden among these populations. Interdisciplinary approaches and community-based strategies are needed in this area.

TRANSPORT-RELATED INJURIES

Transport-related injuries constitute between 5% and 13% of all ocular trauma (see Table 2). Motor vehicle crashes account for between 10% and 13% of principal discharge diagnoses and more than 30% of secondary discharge diagnoses of hospitalized ocular injuries.^10,11 These figures demonstrate that isolated ocular injuries are usually the exception in motor vehicle crashes; most severe ocular injuries from these crashes are associated with multiple organ system trauma. Other reports consistently indicate that motor vehicle crashes are an important cause of severe ocular injury, especially among very young children and young adults.^35,58–63 Data from the Eye Injury Registry of Alabama showed that 41% of motor vehicle crash victims with ocular injury were legally blind after at least 3 months of follow-up. Twelve percent of eyes required enucleation.⁶¹ In Israel, a 3-year nationwide study of the incidence of hospitalization for ocular injuries showed that injuries sustained in motor vehicle crashes were associated with the highest ocular morbidity; 34% of these victims were blinded.⁶⁴

Because motor vehicle crash-related eye trauma carries a particularly unfavorable treatment and prognosis, prevention of these injuries is of extraordinary importance. Data suggest that significant reduction in the incidence of motor vehicle-related ocular trauma may be attributed to windshield design modifications and seat belt-wearing habits. In the United States, laminated windshields appear to result in significantly fewer ocular injuries than the tempered glass windshields commonly used in Europe and Asia.^65,66 In Northern Ireland and Great Britain, well-conducted studies have demonstrated a 60% to 73% reduction in motor vehicle-related ocular injuries after the introduction of compulsory seat belt use.^59,60,63 In the National Crash Severity Study conducted by the National Highway Traffic Safety Administration, none of the 86 individuals with ocular injuries identified among 106,000 motor vehicle occupants was wearing a seat belt at the time of the crash.⁶⁵

OTHER ETIOLOGIES AND SETTINGS OF INJURIES

BB and Air Guns

In children less than 15 years of age, national hospital discharge data indicate that 50% of ocular injuries were caused by BB or air guns.¹¹ Although this figure may not be accurate, because only one quarter of all discharge records had etiology coding available,¹¹ the importance of BB or air guns in severe eye injuries among the young cannot be ignored. Other studies suggest that 4% to 8% of all cases of severe eye injury in the pediatric group are caused by nonpower firearms such as BB or air guns.^{9,15,62,67,68} The visual disability associated with these injuries is high, and a significant proportion of eyes are lost completely or are functionally blind after such injuries, despite modern surgical techniques.^69–72 Primary prevention is perhaps the only rational strategy given the poor surgical outcomes associated with these injuries. There has been legislative progress regarding safety labeling and sales of such weapons, but successful interventions in this area have not been demonstrated.

WAR-RELATED INJURIES

Eye injuries among soldiers in combat occur in epidemics during wartime and have profound military implications. In World War II, more than 15,000 soldiers were blinded as a result of ocular trauma.⁷³ During the Vietnam War, more than 1,200 eyes were enucleated.⁷⁴ Beyond the medical implications of eye injuries, otherwise fit and healthy soldiers who sustain these injuries often become unfit for further combat service and many civilian occupations. Only a quarter of American soldiers with eye injuries in Vietnam were able to return to active duty, and a significant proportion required special postwar care and rehabilitation.⁷⁴ Rates of ocular injury during wartime are not readily available; however, the percentage of ocular injuries compared with injuries sustained by other body parts has been increasing with succeeding wars in the twentieth century.⁷⁵ Although eye injuries composed only 2% to 2.5% of all body injuries in World War I and II,^73,76 this percentage was 2.8% in the Korean conflict,⁷⁷ 5% to 9% in Vietnam,⁷⁴ 6% in the Middle East wars,^78,79 and 13% in the recent Persian Gulf war.⁸⁰ Because most injuries were caused by blast fragments or ricochets, multiple intraocular foreign bodies in a single eye were common, and between 15% to 25% of eye injuries were bilateral ocular injuries.⁷⁵ The high proportion of eye injuries may be attributed to the prone posture assumed in combat, the exceptional vulnerability of the eye to small particles that would have minimal effect on other parts of the body, and the preferential exposure of the face in tank warfare. For example, in the Middle East wars, 25% to 40% of eye casualties were among tank crew, although they formed only a small proportion of the total fighting force.^78,79 Two case series of ocular injuries sustained by the U.S. Army during the recent Gulf War highlight some of the causes and types of injuries seen during modern wars.^80,81

Primary prevention through the use of eye protective devices is possible and has been shown to be efficacious.^79,82,83 However, military eye protection programs themselves are less effective; few soldiers given eye armor use it, even during wartime.^75,81 There are a variety of possible reasons why soldiers do not use eye armor.⁸⁴ These include organizational attitude toward eye protection programs in the military, the soldiers' perceptions of eye injury, and beliefs about the efficacy of eye armor. An understanding of these factors will aid future development of more effective strategies in eye injury prevention in the military.

Laser weapon injuries are likely to be an increasingly important cause of ocular trauma in future wars. Mader and associates reported on two cases of presumed laser injury during Operation Desert Storm; one American casualty presented with a left macular burn and another had with bilateral macular burns and a subretinal hemorrhage.⁸¹ With the widespread use of laser weapons on the battlefield, it has been postulated that eye injuries may constitute up to half of all combat injuries in the next century.⁸⁵ The threat of laser weapons in future wars is a matter of concern to the international community⁸⁶ and has prompted the International Committee of the Red Cross and other agencies to propose a ban in 1995 on blinding laser weapons.⁸⁷ Controversy remains as to whether the measures taken will effectively limit the use of these weapons.

FIREWORKS

Another well known cause of ocular injuries is fireworks.^88–90 Although they account for only a small proportion of severe ocular injuries in the population, they usually occur in children. The ability to predict their occurrence (usually during the days around the fourth of July and other holidays) and prevent such injuries make them of particular significance. Fireworks-related injuries can be as severe as blast injuries seen in warfare among soldiers.^89,90 The number of injuries is increasing, from 4700 total injuries in 1976 to more than 11,000 in 1981,^90,91 in part because of the failure to pass national legislation strictly regulating the sale of fireworks. In the absence of foreseeable future laws relating to their sale and use, efforts must be directed at educating the public, and especially young children, about the risks associated with fireworks.

CONSUMER PRODUCT-RELATED OCULAR INJURIES

An area of growing concern in the epidemiology of ocular trauma is consumer-related injuries, such as infective keratitis associated with contact lens wear.⁹² The absolute risk of infective keratitis among contact lens users varies by type of lens and wearing habits, and is estimated to be between 1 per 300 persons per year to 1 per 2500 persons per year. The increasing widespread use of lenses, with wearing patterns that include overnight use, and the fact that lenses are often prescribed for cosmetic reasons make almost any excess risk an important issue.^92–94 New lens materials with higher oxygen transmission to the corneal epithelium, and continued recommendations regarding the elimination of overnight wear can limit the potentially blinding consequences associated with corneal ulceration. Excluding contact lens-related infective keratitis, consumer product-related ocular trauma has not been well characterized. A large study showed that in 1991 alone, there were nearly 300,000 consumer product-related eye injuries treated in hospital emergency rooms, with nearly 500 different products implicated in these injuries.⁹⁵ The leading causes were contact lenses, which accounted for more than 25,000 emergency room visits, followed by welding equipment, hair curlers and curling irons, and workshop power grinders.

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